Process for the regeneration of a catalyst plant and apparatus for performing the process

ABSTRACT

A gas stream containing e.g. molecular hydrogen is used for the regeneration of a catalyst for NOx and SO2 removal from the flue gas of a gas turbine. In order to reduce the consumption of regeneration gas, the gas inlet is located between the SCOSOx catalyst ( 2 ) and the SCONOx catalyst ( 3 ). The regeneration gas leaves the catalyst chamber upstream of the SCOSOx catalyst and is recycled. For the regeneration of the SCONOx catalyst and to keep SO2 containing gas from entering the SCONOx catalyst, a second regeneration gas inlet is located downstream of the SCONOx catalyst. The regeneration gas entering the catalyst chamber through this port passes the SCONOx ( 3 ) and the SCOSOx catalyst ( 2 ). The direction of the flow in the SCONOx catalyst can also be reversed. In another example, regeneration gas outlets are located both upstream of the SCOSOx and downstream of the SCONOx catalyst. But, only the regeneration gas from the SCONOx catalyst is recycled.

This application is related to and claims priority under 35 U.S.C. § 119to German Patent Application No. 100 49 040.9, filed Oct. 4, 2000, theentire contents of which are incorporated by reference herein. Inaddition, this application is a divisional of U.S. patent applicationSer. No. 09/969,769 filed on Oct. 4, 2001, now U.S. Pat. No. 6,946,419,the entire contents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a process for the regeneration of a catalystplant for the removal of SO2 and NOx from the flue gas of a gas turbine,and also to an apparatus for carrying out the process.

BACKGROUND OF THE INVENTION

It has been known for a long time to reduce the SO2 content and the NOxcontent of the flue gases from gas turbines to environmentallyacceptable values by means of catalyst plants which compriserespectively a so-called SCOSOx catalyst for the removal of SO2 and,downstream of this, a SCONOx catalyst for the removal of NOx. Thecatalysts are relatively rapid in their effect, and it is likewise knownto regenerate them by means of substantially oxygen-free regeneratinggas which is passed through them to restore their effectiveness.

Thus the use of a regenerating gas for the regeneration of a SCONOxcatalyst is described in U.S. Pat. No. 5,762,885, and the gas contains4% of molecular hydrogen as the active substance; the rest is a carriergas, which principally consists of steam and contains small amounts ofmolecular nitrogen and carbon dioxide. If the regenerating gas is passedonly once through the catalyst, a very high consumption results, andcorrespondingly high costs arise. In the described case, the productionof the steam is costly in energy and correspondingly expensive,especially as demineralized water is required for its production. In theabove reference, it is also proposed to utilize used regenerating gas ascarrier gas. In a closed circuit of regenerating gas through a catalystplant, which also contains a SCOSOx catalyst, the SO2 released in itsregeneration would however poison the SCONOx catalyst.

SUMMARY OF THE INVENTION

The invention has as its object to provide a process of the categoryconcerned, in which the consumption of regenerating gas is substantiallyreduced, without having to take account of the danger of a poisoning ofthe SCONOx catalyst by SO2. In one embodiment, the process extracts aregenerating gas from upstream of a SCOSOx catalyst or from between aSCOSOx catalyst and a SCONOx catalyst, introduces the extractedregenerating gas between the SCOSOx catalyst and the SCONOx catalyst orupstream of the SCOSOx catalyst, and introduces a fresh regenerating gasdownstream of the SCONOx catalyst.

In an additional embodiment, the process extracts a regenerating gasfrom downstream of a SCONOx catalyst, introduces the extractedregenerating gas between a SCOSOx catalyst and the SCONOx catalyst, andextracts and removes the regenerating gas from upstream of the SCOSOxcatalyst.

Furthermore, suitable apparatus is provided for carrying out theprocess. In one embodiment, an apparatus for regenerating catalyst in acatalyst plant comprises a catalyst plant, at least one supply pipe forthe introduction of regenerating gas, at least one drain pipe for theextraction of regenerating gas, and a further supply pipe for the supplyof fresh regenerating gas.

The invention provides a process of the category concerned, in which theregenerating gas is partially conducted in a closed circuit and hence isvery well utilized, but transmission of the SO2 arising from the SCOSOxcatalyst into the SCONOx catalyst is reliably prevented. The consumptionof regenerating gas is substantially reduced, with a resulting costsavings in each case, but particularly when it consists of steam to alarge extent.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are disclosed in the followingdescription and illustrated in the accompanying drawings, in which:

FIG. 1 shows schematically an apparatus according to the invention forcarrying out the process according to the invention according to a firstembodiment.

FIG. 2 shows schematically an apparatus according to the invention forcarrying out the process according to the invention, according to asecond embodiment.

DETAILED DESCRIPTION OF THE INVENTION

An apparatus according to the invention comprises (FIG. 1) a catalystplant with a catalyst chamber 1, through which a portion of the flue gasof a gas turbine operated with natural gas, oil, synthesis gas or thelike is conducted to a chimney, and in the latter, arranged insuccession in the flow direction, a SCOSOx catalyst 2 for the removal ofSO2 and a SCONOx catalyst 3 for the removal of NOx from the flue gas. Bymeans of a first damper 4 arranged upstream and a second damper 5arranged downstream, the SCOSOx catalyst 2 and the SCONOx catalyst 3 canbe shut off from the flue gas stream.

A supply pipe 7 opens via an inlet valve 6 into the catalyst chamber 1between the SCOSOx catalyst 2 and the SCONOx catalyst 3, and a supplypipe 9 opens into it via a feed valve 8. A steam reforming catalyst 10is situated in the supply pipe 7 between the outlet of the supply pipe 9and the feed valve 8. A drain pipe 12 leads via an outlet valve 11 fromthe catalyst chamber 1 between the first damper 4 and the SCOSOxcatalyst 2, and from there branches a supply pipe 13 leading to ahydrogen monitor and an oxygen monitor. The drain pipe 12 is connectedvia a pump 14 to the supply pipe 7. A drain 15 branches off between thepump 14 and the outlet of the supply pipe 9 in the supply pipe 7.

A further supply pipe 17 opens via a supply valve 16 between the SCONOxcatalyst 3 and the second damper 5, and a further supply pipe 19 opensinto it. A steam reforming catalyst 20 is situated between the outlet ofthe supply pipe 19 and the feed valve 16, and a purge duct 22 opens viaa purge valve 21.

When the catalyst plant is in operation, the dampers 4, 5 are open, andthe valves 6, 11, 8 and 18 are closed. After about twenty minutes, theeffect of the catalyst plant diminishes, and it has to be regenerated.For this purpose, the dampers 4, 5 are closed—the corresponding portionof the flue gas is meanwhile passed through other catalyst plants —andthe outlet valve 11 and the feed valve 16 are opened. Furthermore, thepurge valve 21 is opened, and a substantially oxygen-free cleaning gas,e.g., carrier gas, as described hereinafter, is supplied through thepurge duct 22, driving the oxygen-containing flue gas out from thecatalyst plant through the drain pipe 12, the pump 14, and the drain 15.The oxygen monitor connected via the supply pipe 13 indicates when theoxygen content has fallen so far that the purge process can beinterrupted.

After closing the purge valve 21, a carrier gas such as steam, forexample, is conducted into the catalyst plant via the supply pipe 17,and has natural gas mixed with it from the supply pipe 19 by opening thefeed valve 18. On flowing through the regenerating catalyst 20, aportion of the hydrocarbons contained in the natural gas is convertedinto molecular hydrogen. On flowing through the SCONOx catalyst 3 andthen the SCOSOx catalyst 2, these are regenerated, chiefly by the actionof the hydrogen. Furthermore, the valves 6 and 8 are opened, thus makinga connection to the pump 14, so that regenerat-ing gas drawn off via thedrain pipe 12, and replaced as required by natural gas from the supplypipe 9 via the valve 8, and conducted back into the catalyst chamber 1via the supply pipe 7. It then passes the steam reforming catalyst 10,where hydrocarbons are further converted into molecular hydrogen.

A flow is then maintained for as long as required, and includes asubstantially closed circuit flow through the supply pipe 7, the SCOSOxcatalyst 2 and the drain pipe 12, maintained by the pump 14. Onto thiscircuit flow there is superposed a linear flow, which leads from thesupply pipe 17, through which fresh regenerating gas flows, through theSCONOx catalyst 3 and the SCOSOx catalyst 2, to the drain pipe 12. Thelast-named flow prevents regenerating gas which has already flowedthrough the SCOSOx catalyst 2 and therefore contains SO2, from reachingthe SCONOx catalyst 3 out of the supply pipe 7. Respectively as muchregenerating gas is drawn off through the drain 15 as is fed in throughthe supply pipe 17.

The supply of natural gas from the supply pipe 9 is regulated based onthe measurement of the H2 content of the regenerating gas by means ofthe hydrogen monitor connected via the supply pipe 13. If theregeneration is shut off from the catalyst plant, the valves 6, 11, 16,and also 8, 18, are closed, and the dampers 4, 5 are opened again.

In this embodiment of the process according to the invention, the volumeflow through the SCOSOx catalyst 2 corresponds to the sum of the volumeflow through the SCONOx catalyst 3 and the volume flow of the returnedregenerating gas. Since in the interest of as great as possible asavings of regenerating gas, the portion of the first should be as smallas possible, this embodiment is particularly suitable when theregeneration requirement of the SCOSOx catalyst 2 considerably exceedsthat of the SCONOx catalyst 3.

The arrangement consisting of the drain pipe 12, the pump 14 and thesupply pipe 7 and also the parts and ducts connected thereto can also bearranged in a mirror-image manner, such that the drain pipe 12 opensbetween the SCOSOx catalyst 2 and the SCONOx catalyst 3, and the supplypipe 7 upstream of the SCOSOx catalyst 2. The flow direction in theportion of the catalyst containing the SCOSOx catalyst 2 would then bereversed, and the regenerating gas introduced through the supply pipe 17would not flow directly through the SCOSOx catalyst 2, without thefunctioning of the apparatus being thereby substantially impaired.

A differing embodiment of the apparatus according to the invention isshown in FIG. 2. It is somewhat converted or simplified in a fewadditional points in contrast to the embodiment of FIG. 1, but canhowever be modified or supplemented to correspond to this embodiment,and vice versa. Corresponding parts have the same reference numerals inboth Figures.

Here also, a catalyst plant includes a catalyst chamber 1, through whicha portion of the flue gas of a gas turbine operated with natural gas isconducted to a chimney, and in the latter, arranged in succession in theflow direction, a SCOSOx catalyst 2 for removal of SO2 and a SCONOxcatalyst 3, consisting of several sections, for the removal of NOx fromthe flue gas. The SCOSOx catalyst 2 and the SCONOx catalyst 3 can againbe excluded from the flue gas stream by means of a first damper 4arranged upstream and a second damper 5 arranged downstream.

Here also, a supply pipe 7, into which a further supply pipe 9 opens,opens into the catalyst chamber 1 between the SCOSOx catalyst 2 and theSCONOx catalyst 3. A drain pipe 12 leads out of the catalyst chamber 1via an outlet valve between the first damper 4 and the SCOSOx catalyst2. Furthermore, a drain pipe 23 leaves between the SCONOx catalyst 3 andthe second damper, and leads via an outlet valve 24 and a pump 14 to thesupply pipe 7, into which it opens outside the supply pipe 9. Therebranch off from the drain pipe 23, still within the outlet valve 24, asupply pipe 13, which leads to an oxygen monitor and a hydrogen monitor,and also a purge duct 22 via a purge valve 21.

For regeneration of the catalyst plant, the dampers 4, 5 are againclosed, and the valves 6, 11 and 21 are first opened and a substantiallyoxygen-free carrier gas, e.g., steam, is introduced as cleaning gas andpurges the catalyst plant, until the oxygen monitor connected to thesupply pipe 13 establishes a sufficiently low oxygen content. Theexpelled flue gas then escapes via the drain pipe 12 and also the drainpipe 23 and the purge duct 22. The purge valve 21 is then closed and theoutlet valve 24 is opened. Further carrier gas is conducted into thecatalyst plant via the supply pipe 7, molecular hydrogen being addedthrough the supply pipe 9, supplementing the carrier gas to giveregenerating gas.

A substantially closed circuit flow is again developed from the supplypipe 7 through the SCONOx catalyst 3 and the drain pipe 23 via the pump14 and back to the supply pipe 7, and also a linear flow from the supplypipe 7 through the SCOSOx catalyst 2 to the drain pipe 12, by means ofwhich regenerating gas which has taken up SO2 in the SCOSOx catalyst 2is extracted and removed. The removed regenerating gas is replaced byfresh.

Since the circuit flow is conducted through the SCONOx catalyst 3, thevariant embodiment of the process is suitable from the standpoint of aconsiderable savings of regenerating gas, above all when theregeneration requirement of the latter is considerably greater than thatof the SCOSOx catalyst 2, so that, e.g., between 80% and 90% of thetotal volume flow through the catalyst plant passes through the SCONOxcatalyst 3.

Other than steam, both embodiments of the process according to theinvention can also use as the carrier gas, molecular nitrogen,oxygen-poor flue gas of a gas burner, or else exhaust gas of an internalcombustion engine operated with natural gas, gasoline, propane, or thelike, preferably a piston engine, the power of which is used in the samemanner as that of the gas turbine, and thus as a rule for electric powergeneration.

1. Apparatus for regeneration of a catalyst plant comprising: a catalystfor the removal of SO2, and arranged downstream thereof, a catalyst forthe removal of NOx, from the flue gas of a gas turbine, and also atleast one supply pipe for the introduction of regenerating gas, and atleast one drain pipe for the extraction of regenerating gas, wherein thesupply pipe opens between the catalyst for the removal of SO2 and thecatalyst for the removal of NOx, and is connected to the drain pipewhich leaves upstream of the catalyst for the removal of SO2, and afurther supply pipe for the supply of fresh regenerating gas is presentand opens downstream of the catalyst for the removal of NOx. 2.Apparatus according to claim 1, wherein at least one supply pipe for theaddition of molecular hydrogen or hydrocarbon opens into at least one ofthe supply pipe for the introduction of regenerating gas and the furthersupply pipe for the supply of fresh regenerating gas.
 3. Apparatusaccording to claim 2, wherein: a steam reforming catalyst is situatedbetween an opening of the at least one supply pipe for the addition ofmolecular hydrogen or hydrocarbon that opens into the supply pipe forthe introduction of regenerating gas, and an opening of the supply pipefor the introduction of regenerating gas that opens between the catalystfor the removal of SO2 and the catalyst for the removal of NOx; and/or asteam reforming catalyst is situated between an opening of the at leastone supply pipe for the addition of molecular hydrogen or hydrocarbonthat opens into the further supply pipe for the supply of freshregenerating gas, and an opening of the further supply pipe for thesupply of fresh regenerating gas that opens downstream of the catalystfor the removal of NOx.
 4. Apparatus according to claim 1, wherein apurge duct for the supply or removal of a cleaning gas opens into atleast one supply pipe or drain pipe.
 5. Apparatus according to claim 1,wherein at least one drain pipe is connected to a hydrogen monitor andto an oxygen monitor.
 6. Apparatus according to claim 1, furthercomprising a purge duct for the supply or removal of a cleaning gas, thepurge duct opening into the drain pipe.
 7. Apparatus according to claim1, wherein the at least one drain pipe is connected to a hydrogenmonitor and to an oxygen monitor.
 8. Apparatus for regeneration of acatalyst plant comprising: a catalyst plant with a catalyst for theremoval of SO2, and arranged downstream thereof, catalyst for theremoval of NOx, from the flue gas of a gas turbine, and also at leastone supply pipe for the introduction of regenerating gas, and at leastone drain pipe for the extraction of regenerating gas, wherein thesupply pipe opens upstream of the catalyst for the removal of SO2 and isconnected to the drain pipe which leaves between the catalyst for theremoval of SO2 and the catalyst for the removal of NOx, and a furthersupply pipe for the supply of fresh regenerating gas is present andopens downstream of the catalyst for the removal of NOx.
 9. Apparatusaccording to claim 8, wherein at least one supply pipe for the additionof molecular hydrogen or hydrocarbon opens into at least one of thesupply pipe for the introduction of regenerating gas and the furthersupply pipe for the supply of fresh regenerating gas.
 10. Apparatusaccording to claim 9, wherein: a steam reforming catalyst is situatedbetween an opening of the at least one supply pipe for the addition ofmolecular hydrogen or hydrocarbon that opens into the supply pipe forthe introduction of regenerating gas, and an opening of the supply pipefor the introduction of regenerating gas that opens upstream of thecatalyst for the removal of SO2; and/or a steam reforming catalyst issituated between an opening of the at least one supply pipe for theaddition of molecular hydrogen or hydrocarbon that opens into thefurther supply pipe for the supply of fresh regenerating gas, and anopening of the further supply pipe for the supply of fresh regeneratinggas that opens downstream of the catalyst for the removal of NOx. 11.Apparatus according to claim 8, wherein a purge duct for the supply orremoval of a cleaning gas opens into at least one supply pipe or drainpipe.
 12. Apparatus according to claim 8, wherein at least one drainpipe is connected to a hydrogen monitor and to an oxygen monitor. 13.Apparatus according to claim 8, further comprising a purge duct for thesupply or removal of a cleaning gas, the purge duct opening into thedrain pipe.
 14. Apparatus according to claim 8, wherein the at least onedrain pipe is connected to a hydrogen monitor and to an oxygen monitor.15. Apparatus for regeneration of a catalyst plant comprising: acatalyst plant with a catalyst for the removal of SO2, and arrangeddownstream thereof, a catalyst for the removal of NOx, from the flue gasof a gas turbine, and also with at least one supply pipe for theintroduction of regenerating gas, and at least one drain pipe for theextraction of regenerating gas, leaving upstream of the catalyst for theremoval of SO2 wherein the supply pipe opens between the catalyst forthe removal of SO2 and the catalyst for the removal of NOx, and isconnected to a further drain pipe arranged downstream of the catalystfor the removal of NOx.
 16. Apparatus according to claim 15, wherein asupply pipe for the addition of molecular hydrogen or hydrocarbon opensinto at least one supply pipe.
 17. Apparatus according to claim 16,wherein a steam reforming catalyst is situated between an opening of theat least one supply pipe for the addition of molecular hydrogen orhydrocarbon that opens into the supply pipe for the introduction ofregenerating gas, and an opening of the supply pipe for the introductionof regenerating gas that opens between the catalyst for the removal ofSO2 and the catalyst for the removal of NOx.
 18. Apparatus according toclaim 15, wherein a purge duct for the supply or removal of a cleaninggas opens into at least one supply pipe or drain pipe.
 19. Apparatusaccording to claim 15, wherein at least one drain pipe is connected to ahydrogen monitor and to an oxygen monitor.
 20. Apparatus according toclaim 15, further comprising a purge duct for the supply or removal of acleaning gas, the purge duct opening into the drain pipe.
 21. Apparatusaccording to claim 15, wherein the further drain pipe is connected to ahydrogen monitor and to an oxygen monitor.
 22. An apparatus forregenerating catalyst in a catalyst plant, the apparatus comprising: acatalyst plant comprising a catalyst for the removal of SO2 and at leastone catalyst for the removal of NOx, the catalyst for the removal of SO2upstream of the at least one catalyst for the removal of NOx, a firstsupply pipe in fluid communication with the catalyst plant at a firstintroduction point downstream of the at least one catalyst for theremoval of NOx to introduce a regeneration gas into the catalyst plant;at least one drain pipe in fluid communication with the catalyst plantat a first extraction point upstream of the catalyst for the removal ofSO2 or between the catalyst for the removal of SO 2 and the at least onecatalyst for the removal of NOx; and a second supply pipe in fluidcommunication with the catalyst plant at a second introduction pointseparated from the at least one drain pipe by the catalyst for theremoval of SO2.